Poor insulation vapor retarder or vapor barrier in wood stud construction

Hello,

I want to renovate our bathroom. Our house is built with a timber frame construction with glass wool and gypsum fiber boards (Fermacell).
My ideas are:

- to replace the glass wool with wood fiber insulation
- to use OSB boards and gypsum fiber boards again on top as cladding --> more stable walls for subsequent tiles
- I am not sure whether and where I should use a vapor barrier or even a vapor retarder foil between the insulation and the cladding

Is all this okay for a bathroom?

Regards
Alex